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MA12.05 - Can Tumor Spread through Air Spaces (STAS) in Lung Adenocarcinomas Be Predicted Pre- and Intraoperatively? (ID 6026)

Background: We and others have reported the prognostic impact of tumor spread through air spaces (STAS) in lung adenocarcinomas. The goal of this study is to investigate preoperative predicting factors for STAS and to determine whether STAS can be detected by intraoperative frozen section analysis.

Methods: In a cohort of 874 patients with small (≤2cm) stage I adenocarcinoma (1995-2012), we reviewed preoperative computed tomography (CT) and positron emission tomography (PET) scans. According to the 2016 Fleischner Society’s criteria, radiological whole tumor size, consolidation size, as well as C/T ratio (consolidation/whole tumor diameter) were determined using thin slice (<3mm) CT scans where available (n=174). Clinico-radiological prediction of STAS was evaluated by logistic regression model. Using the frozen section slides with adequate adjacent lung parenchyma surrounding tumor without artifact (n=48), the presence of STAS was evaluated by five pathologists who are unaware of the radiological findings or the pathological information on permanent slides. The kappa statistic was calculated to measure the agreement between two pathologists.

Results: In univariable model for predicting STAS, current smoker, larger consolidation tumor size, C/T ratio, and SUVmax were significant variables. In multivariable model, current smoker and C/T ratio were independent risk factors for the presence of STAS (p=0.027 and p<0.001, respectively; Table 1a). The sensitivity and the specificity of frozen section for prediction of STAS were 71% (95% confidence interval: 52-91%), 92.4% (81-100%) respectively, and the accuracy was 80% (71-89%). The kappa statistics were 0.40-0.74 (Table 1b) with 8/10 being moderate or substantial agreement.

Conclusion: Smoking status and C/T ratio were independent predictors for the presence of STAS in patients with small lung adenocarcinomas. Frozen section prepared with adequate surrounding normal lung tissue may help identify STAS intraoperatively. Figure 1

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Background: Stereotactic body radiation therapy (SBRT) has emerged as an effective treatment for early-stage lung cancer. Histologic subtyping in surgically resected lung adenocarcinomas is recognized as a prognostic factor, with the presence of solid or micropapillary patterns predicting poor outcomes. Herein, we describe outcomes following SBRT for early-stage lung adenocarcinoma by histologic subtype.

Methods: We identified 119 consecutive patients (124 lesions) with stage I-IIA lung adenocarcinoma who were treated with definitive SBRT at our institution between August 2008 and August 2015 and had undergone core biopsy. Histologic subtyping was performed according to the 2015 WHO Classification. Thirty-seven tumors (30%) were of high risk subtype, defined as containing a component of solid and/or micropapillary pattern. Cumulative incidences of local, nodal, regional and distant failure were compared between high risk vs. non-high risk adenocarcinoma subtypes with Gray’s test, and multivariable-adjusted hazard ratios were estimated from propensity score-weighted Cox regression models.

Conclusion: Outcomes following SBRT for early-stage adenocarcinoma of the lung are highly correlated with histologic subtype, with micropapillary and solid tumors portending significantly higher rates of locoregional and metastatic progression. In this context, histologic subtype based on core biopsies is a novel prognostic factor and may have important implications for patient selection, adjuvant treatment, biopsy methods and clinical trial design.

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